Abstract

We investigate excitonic carrier diffusion in both bulk ZnO and nanorods (NRs). Using time-resolved differential reflectivityspectroscopy, we observe a fast decaying component together with a longer exponential relaxation. In bulk ZnO, we find that the fast decay term (∼1 ps) originates from excitonic diffusion along the growth direction. By probing at both the A and B excitons, we find different diffusion coefficients for each. In ZnOnanorods, the diffusion contribution is missing. We attribute this to two effects: (1) defects in the nanorods substantially slow the diffusion process and (2) excitons in nanorods are generated more uniformly than in bulk.

Received 26 October 2011Accepted 08 February 2012Published online 29 February 2012

Acknowledgments:

This work was supported by the Basic Science Program through NRF-2009-0090559, the Bio-Imaging Research Center, “Fusion-Tech. Developments for THz Information and Communications” program of GIST in 2010 and by the NSF through DMR-0706313 and DMR-1105437.